The present invention relates to a machine for finishing flat surfaces such as concrete or cement floors, or floors of similar hardened materials.
Known concrete finishing machines as a rule are equipped with a circular grinding wheel having an axis of rotation perpendicular to the surface to be finished (i.e. so that the grinding wheel lies flat on the floor), and a pair of running wheels. The weight of the machine is carried by the two running wheels and the flat floor-abutting surface of the grinding wheel. The grinding wheel rotates against the floor during machine operation, and the portion of the machine weight over the grinding wheel supplies the necessary downward pressure to finish the surface. However, since the grinding wheel rotates, torque is generated by the grinding wheel due to its frictional contact with the concrete surface, which torque must be absorbed by the operator of the machine to keep the machine steady.
Thus, in known grinding machines, since the grinding wheel itself acts as the third support point, in conjunction with the two running wheels, for supporting the weight of the machine, the torque generated by the grinding wheel has to be absorbed by the operator. On small grinding machines, with low grinding pressure, these forces may be small and considered a minor inconvenience to the operator. In larger machines, however, but also even on small machines when operated over lengthy periods of time, these forces constitute a major ergonomic inconvenience.
In order to counteract to some extent this inconvenience, which makes the machine more difficult to handle and maneuver, some machines are equipped with two counter-rotating grinding wheels. However, under some conditions, for example irregularities in the floor, the torque generated by the grinding wheels is not fully counterbalanced and thus not entirely eliminated. In addition, the use of double grinding wheels renders the machine heavy and difficult to maneuver.
Grinding machines, either having a single grinding wheel or a pair of counter-rotating grinding wheels, normally lack any means of regulating the pressure of the grinding wheels on the underlying surface, which limits the use to which a machine can be put to one particular type of grinding work.